The present invention relates to an active matrix-addressed liquid-crystal display device with separate electrodes at each picture element for driving a liquid crystal. Recently an active matrix-addressed liquid-crystal display device capable of displaying complicated characters and pictures has been developed by the use of a liquid crystal driven with low power. A simple matrix voltage averaging drive system, in which a liquid crystal is driven with an effective voltage between row electrodes and column electrodes, generally gives a picture with low resolution due to a limitation of the number of scanning lines. To obtain a picture with high resolution, an active matrix-addressed drive system should be applied, in which switching transistors are provided for each picture element using a sophisticated semiconductor technique on a semiconductor substrate. In such a case however, only one or a limited number of panels can be fabricated from a silicon wafer serving as a semiconductor substrate, and this results in a high cost of production because of the low yield.
FIG. 1 shows an equivalent circuit diagram of a conventional active matrix-addressed liquid-crystal panel. To improve the resolution, the number of n and m is generally 200-250. The circuit in FIG. 1 is formed on an N-type semiconductor substrate, and MOS transistors M.sub.11, M.sub.12, . . . M.sub.mn are P channel MOS transistors. When image signals or signal voltages are supplied to column electrodes X.sub.1, X.sub.2, . . . X.sub.n, a voltage V.sub.SS negative with respect to a substrate voltage V.sub.DD is a applied to a row electrode Y.sub.1 serving as a gate for each of the MOS transistors M.sub.11, M.sub.12, . . . M.sub.1n so that the image signals are supplied to electric charge storage capacitors C.sub.11, C.sub.12, . . . C.sub.1n, having electrodes for driving a liquid crystal. As a result, the transistors M.sub.11, M.sub.12, . . . M.sub.1n, are turned on and the image signals or signal voltages are written in the capacitors C.sub.11, C.sub.12, . . . C.sub.1n. When the image signals are sufficiently written, the substrate voltage V.sub.DD is applied to the row electrode Y.sub.1 to turn off the MOS transistors M.sub.11, M.sub.12 . . . M.sub.1n to retain the image signals. Afterwards, new image signals are applied to the column electrodes X.sub.1, X.sub.2 . . . X.sub.n again, and the voltage V.sub.SS is applied to a row electrode Y.sub.2 to turn on transistors M.sub.21, M.sub.22, . . . M.sub.2n, and the new image signals are written in capacitors C.sub.21, C.sub.22, . . . C.sub.2n, corresponding to each the transistor. Repeating the above operation, the MOS transistors provided at each of the picture elements of the panel are addressed in turn, whereby the image signals are held in the electric charge storage capacitors provided in couple with the MOS transistors, and the liquid crystal is driven with the driving electrode which maintains the same electric potential.
In this construction the row electrodes Y.sub.1, Y.sub.2, . . . Y.sub.m extend from one end of the panel to the other, the length and the area of the row electrodes being sufficiently long and large in comparison with general IC patterns. As a result there may be a short between the row electrodes and the substrate due to a pinhole in the insulator on the gate or field area. Moreover, if the breakdown voltage sufficiently drops due to junction defects at a protective diode provided at an input portion of the row electrode for preventing breakdown of the gate insulator caused by static electricity, a row electrode Y.sub.i no longer serve as a gate of the MOS transistors M.sub.i1, M.sub.i2, . . . M.sub.in belonging to the row electrode Y.sub.i. The above-noted defects of the gate row electrode appear clearly as a line defect in a distinctly different color from the adjacent rows. Thus the whole panel may lose its value as product by a single line defect. Therefore, almost 100% yield is required for the panel and the cost per 1 panel necessarily becomes higher because only one or more panels using the semiconductor substrate of the active matrix-addressed liquid crystal display device can be fabricated from a silicon wafer by its limited space as described before.